Align & Distribute
Select two or more nodes - shift-drag a box round them, or shift-click them one at a time - and line them up or space them out. This is the tidy-up pass every drawing tool has, and it writes nothing but Node.Position, so it composes with undo, extents and sub-flows.
Distribute keeps the two outermost nodes where they are and evens out the gaps
between everything else. Pack ignores the span and lays them out from the first
node at a fixed gap.